If you are going to use Twinax cables with your Nexus 5000 series switches or Nexus 2000 series FEXes you can check the certification matrix here:
As a bonus sector, data sheet for the 10G SFP+ modules is found in http://www.cisco.com/en/US/prod/collateral/modules/ps5455/data_sheet_c78-455693.html.